Re: [PATCH 2/3] wifi: ath12k: Optimize the lock contention of used list in Rx data path

Karthikeyan Periyasamy
2024-03-19T09:38:03Z

On 3/18/2024 11:39 PM, Kalle Valo wrote:
> Karthikeyan Periyasamy <quic_periyasa@quicinc.com> writes:
>
>> On 3/11/2024 6:35 PM, Kalle Valo wrote:
>>> Karthikeyan Periyasamy <quic_periyasa@quicinc.com> writes:
>>>
>>>> When a packet arrives in Rx rings, the RX descriptor moves from the used
>>>> list to the free list. Then, the rxdma ring gets replenished, where the Rx
>>>> descriptor again moves from the free list to the used list. At the end, the
>>>> descriptor came to the used list with unnecessary list movement. The
>>>> descriptor used list is maintained in the Rxdma ring structure, which
>>>> creates lock contention for the list operations (add, delete) in the Rx
>>>> data path. Optimize the Rx data path by removing the used list from the
>>>> common Rxdma ring and maintain as a local variable in the Rx ring handler
>>>> itself, which avoid lock contention. Now, to find the used list descriptor
>>>> during descriptor cleanup, we need to check the in_use flag for each Rx
>>>> descriptor.
>>>>
>>>> Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1
>>>>
>>>> Signed-off-by: Karthikeyan Periyasamy <quic_periyasa@quicinc.com>
>>> Before looking at this in detail: When optimising something it would be
>>> good to have before and after numbers showing the improvement. Otherwise
>>> it's just wishful thinking.
>> I don't have numbers. Like you said, Its just a wishful think.
> So do you still want us to take this?
>
> In the future please do provide numbers to show that the optimisation
> really helps as intended. Otherwise we might even go backwards.

This is a simple UDP UL throughput test case results on x86+NUC device
with QCN9274 card

Before:
Average:     CPU    %usr   %nice    %sys %iowait    %irq   %soft %steal
%guest  %gnice   %idle
Average:     all    0.24    0.00   12.54    0.08    0.00 23.33
0.00    0.00    0.00   63.81

After:
Average:     CPU    %usr   %nice    %sys %iowait    %irq   %soft %steal
%guest  %gnice   %idle
Average:     all    0.34    0.00    4.60    0.00    0.00 19.59
0.00    0.00    0.00   75.47

is it fine to capture in the commit log ?

--

Karthikeyan Periyasamy
--
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